1. Field of the Invention
The present invention relates to a method of switching a zone through which services are provided to subscriber stations (SS) in an environment using an FRF-1 zone and an FRF-3 zone based on traffic load of each zone in order to reduce the inter-cell interference in 802.16/WiBro systems, and more particularly, to a service zone switching method based on load considering inter-cell interference in 802.16/WiBro systems capable of minimizing the inter-cell interference, enhancing the capacity of cells and improving users' transmission quality in the cells by determining whether the services are provided through one out of an FRF-1 zone (a zone where users can use all subchannels) and an FRF-3 zone (a zone where users can use one third of all subchannels; dividing all channels into 3 channel groups), which are present in one frame, based on the distribution and traffic load of subscriber stations (SS) present in one cell, which consists of 3 sector units, under the environment of the 802.16/WiBro systems and providing services through the selected zone.
2. Description of the Related Art
As known to those skilled in the art, when all cells share the same frequency channels in the deployment of networks, the cells affect quality of used frequency channels in a wireless cellular system, which is called “interference.” Then, such interference affects the capacity and coverage of the cells, which makes it difficult to provide satisfactory transmission quality to users.
In the case of conventional cellular networks, there have been various attempts to minimize interference between cells. For example, there is a channel assignment algorithm for assigning channels so that the channels used by just adjacent cells are not overlapped with each other. Also, there has been much research on a permutation technique of grouping subcarriers into channels in order to minimize overlapping of the channels used by adjacent cells under the environment of systems (i.e. OFDMA) that can assign the subcarriers into time and frequency domains.
Also as an alternative to reduce the interference, there has been an attempt to minimize the inter-cell interference by dividing an FRF method into an FRF-1 method where users in 3 sectors of one cell use the entire frequency bandwidth range and an FRF-3 method where users in each of 3 sectors of one cell use one third of frequency bandwidth range.